Yeast can express and assemble bacterial secretins in the mitochondrial outer membrane
Authors:Janani Natarajan1, Anasuya Moitra1, Sussanne Zabel1,§, Nidhi Singh2, Samuel Wagner2,3 and Doron Rapaport1
doi: 10.15698/mic2020.01.703
Volume 7, pp. 15 to 27, published 19/11/2019.
1 Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany.
2 Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Tübingen, Germany.
3 German Center for Infection Research (DZIF), partner-site Tübingen, Tübingen, Germany.
§ Current address: Center for Bioinformatics (ZBIT), University of Tübingen, Tübingen, Germany.
Keywords:
InvG, mitochondria, outer membrane, protein sorting, PulD, Secretins, SsaC
Corresponding Author(s):
Conflict of interest statement:
The authors declare no conflict of interests.
Please cite this article as:
Janani Natarajan, Anasuya Moitra, Sussanne Zabel, Nidhi Singh, Samuel Wagner and Doron Rapaport (2019). Yeast can express and assemble bacterial secretins in the mitochondrial outer membrane. Microbial Cell 7(1): 15-27. doi: 10.15698/mic2020.01.703
© 2019 Natarajan et al. This is an open-access article released under the terms of the Creative Commons Attribution (CC BY) license, which allows the unrestricted use, distribution, and reproduc-tion in any medium, provided the original author and source are acknowledged.
Abstract:
Secretins form large multimeric pores in the outer membrane (OM) of Gram-negative bacteria. These pores are part of type II and III secretion systems (T2SS and T3SS, respectively) and are crucial for pathogenicity. Recent structural studies indicate that secretins form a structure rich in β-strands. However, little is known about the mechanism by which secretins assemble into the OM. Based on the conservation of the biogenesis of β-barrel proteins in bacteria and mitochondria, we used yeast cells as a model system to study the assembly process of secretins. To that end, we analyzed the biogenesis of PulD (T2SS), SsaC (T3SS) and InvG (T3SS) in wild type cells or in cells mutated for known mitochondrial import and assembly factors. Our results suggest that secretins can be expressed in yeast cells, where they are enriched in the mitochondrial fraction. Interestingly, deletion of mitochondrial import receptors like Tom20 and Tom70 reduces the mitochondrial association of PulD but does not affect that of InvG. SsaC shows another dependency pattern and its membrane assembly is enhanced by the absence of Tom70 and compromised in cells lacking Tom20 or the topogenesis of outer membrane β-barrel proteins (TOB) complex component, Mas37. Collectively, these findings suggest that various secretins can follow different pathways to assemble into the bacterial OM.